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.TH LFCOMPILE 7 "Aug 24, 2009"
.SH NAME
lfcompile \- large file compilation environment for 32-bit applications
.SH DESCRIPTION
.sp
.LP
All 64-bit applications can manipulate large files by default. The methods
described on this page allow 32-bit applications to manipulate large files.
.sp
.LP
In the large file compilation environment, source interfaces are bound to
appropriate 64-bit functions, structures, and types.  Compiling in this
environment allows 32-bit applications to access files whose size is greater
than or equal to 2 Gbyte ( 2^31 bytes).
.sp
.LP
Each interface named \fIxxx\fR\fB()\fR that needs to access 64-bit entities to
access large files maps to a \fIxxx\fR\fB64()\fR call in the resulting binary.
All relevant data types are defined to be of correct size (for example,
\fBoff_t\fR has a typedef definition for a 64-bit entity).
.sp
.LP
An application compiled in this environment is able to use the
\fIxxx\fR\fB()\fR source interfaces to access both large and small files,
rather than having to explicitly utilize the transitional \fIxxx\fR\fB64()\fR
interface calls to access large files. See the \fBlfcompile64\fR(7) manual page
for information regarding the transitional compilation environment.
.sp
.LP
Applications can be compiled in the large file compilation environment by using
the following methods:
.RS +4
.TP
.ie t \(bu
.el o
Use the \fBgetconf\fR(1) utility with one or more of the arguments listed in
the table below. This method is recommended for portable applications.
.sp

.sp
.TS
box;
c | c
l | l .
\fBargument\fR	\fBpurpose\fR
_
\fBLFS_CFLAGS\fR	T{
obtain compilation flags necessary to enable the large file compilation environment
T}
\fBLFS_LDFLAGS\fR	obtain link editor options
\fBLFS_LIBS\fR	obtain link library names
\fBLFS_LINTFLAGS\fR	obtain lint options
.TE

.RE
.RS +4
.TP
.ie t \(bu
.el o
Set the compile-time flag \fB_FILE_OFFSET_BITS\fR to 64 before including any
headers. Applications may combine objects produced in the large file
compilation environment with objects produced in the transitional compilation
environment, but must be careful with respect to interoperability between those
objects. Applications should not declare global variables of types whose sizes
change between  compilation environments.
.RE
.SS "Access to Additional Large File Interfaces"
.sp
.LP
The \fBfseek()\fR and \fBftell()\fR functions \fIdo not\fR map to functions
named \fBfseek64()\fR and \fBftell64()\fR; rather, the large file additions
\fBfseeko()\fR and \fBftello()\fR, have functionality identical to
\fBfseek()\fR and \fBftell()\fR and \fIdo\fR map to the 64-bit functions
\fBfseeko64()\fR and \fBftello64()\fR. Applications wishing to access large
files should use \fBfseeko()\fR and \fBftello()\fR in place of \fBfseek()\fR
and \fBftell()\fR. See the \fBfseek\fR(3C) and \fBftell\fR(3C) manual pages for
information about  \fBfseeko()\fR and \fBftello()\fR.
.sp
.LP
Applications wishing to access  \fBfseeko()\fR and \fBftello()\fR as well as
the POSIX and X/Open specification-conforming interfaces should define the
macro \fB_LARGEFILE_SOURCE\fR to be 1 and set whichever feature test macros are
appropriate to obtain the desired environment (see \fBstandards\fR(7)).
.SH EXAMPLES
.sp
.LP
In the following examples, the large file compilation environment is accessed
by invoking the \fBgetconf\fR utility with one of the arguments listed in the
table above. The additional large file interfaces are accessed by specifying
\fB-D_LARGEFILE_SOURCE\fR\&.
.sp
.LP
The examples that use the form of command substitution specifying the command
within parentheses preceded by a dollar sign can be executed only in a
POSIX-conforming shell such as the Korn Shell (see \fBksh\fR(1)). In a shell
that is not POSIX-conforming, such as the Bourne Shell (see \fBsh\fR(1)) and
the C Shell (see \fBcsh\fR(1)), the \fBgetconf\fR calls must be enclosed within
grave accent marks, as shown in the second example.
.LP
\fBExample 1 \fRCompile a program with a "large" \fBoff_t\fR that uses
\fBfseeko()\fR, \fBftello()\fR, and \fByacc\fR.
.sp
.LP
The following example compiles a program with a "large"  \fBoff_t\fR and uses
\fBfseeko()\fR, \fBftello()\fR, and \fByacc\fR(1).

.sp
.in +2
.nf
$ c89 -D_LARGEFILE_SOURCE                \e
      -D_FILE_OFFSET_BITS=64 -o foo      \e
      $(getconf LFS_CFLAGS) y.tab.c b.o  \e
      $(getconf LFS_LDFLAGS)             \e
      -ly $(getconf LFS_LIBS)
.fi
.in -2

.LP
\fBExample 2 \fRCompile a program with a "large" \fBoff_t\fR that does not use
\fBfseeko()\fR and \fBftello()\fR and has no application specific libraries.
.sp
.in +2
.nf
% c89 -D_FILE_OFFSET_BITS=64     \e
      \(gagetconf LFS_CFLAGS\(ga a.c   \e
      \(gagetconf LFS_LDFLAGS\(ga      \e
      \(gagetconf LFS_LIBS\(ga         \e
.fi
.in -2

.LP
\fBExample 3 \fRCompile a program with a "default" \fBoff_t\fR that uses
\fBfseeko()\fR and \fBftello()\fR.
.sp
.in +2
.nf
$ c89 -D_LARGEFILE_SOURCE  a.c
.fi
.in -2

.SH SEE ALSO
.sp
.LP
.BR csh (1),
.BR getconf (1),
.BR ksh (1),
.BR sh (1),
.BR yacc (1),
.BR fseek (3C),
.BR ftell (3C),
.BR lf64 (7),
.BR lfcompile64 (7),
.BR standards (7)
.SH NOTES
.sp
.LP
Certain system-specific or non-portable interfaces are not usable in the large
file compilation environment. Known cases are:
.RS +4
.TP
.ie t \(bu
.el o
Kernel data structures read from \fB/dev/kmem\fR.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Interfaces in the kernel virtual memory library, \fB-lkvm\fR\&.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Interfaces in the \fBELF\fR access library, \fB-lelf\fR\&.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Interfaces to \fB/proc\fR defined in <\fBprocfs.h\fR>.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The \fBustat\fR(2) system call.
.RE
.sp
.LP
Programs that use these interfaces should not be compiled in the large file
compilation environment.  As a partial safeguard against making this mistake,
including either of the <\fBlibelf.h\fR> or <\fBsys/procfs.h\fR> header files
will induce a compilation error when the large file compilation environment is
enabled.
.sp
.LP
In general, caution should be exercised when using any separately-compiled
library whose interfaces include data items of type \fBoff_t\fR or the other
redefined types either directly or indirectly, such as with '\fBstruct
stat\fR'. (The redefined types are \fBoff_t\fR, \fBrlim_t\fR, \fBino_t\fR,
\fBblkcnt_t\fR, \fBfsblkcnt_t\fR, and \fBfsfilcnt_t\fR.) For the large file
compilation environment to work correctly with such a library, the library
interfaces must include the appropriate \fIxxx\fR\fB64()\fR binary entry points
and must have them mapped to the corresponding primary functions when
\fB_FILE_OFFSET_BITS\fR is set to 64.
.sp
.LP
Care should be exercised using any of the \fBprintf()\fR or \fBscanf()\fR
routines on variables of the types mentioned above.  In the large file
compilation environment, these variables should be printed or scanned using
\fBlong long\fR formats.
.SH BUGS
.sp
.LP
Symbolic formats analogous to those found in \fB<sys/int_fmtio.h>\fR do not
exist for printing or scanning variables of the types that are redefined in the
large file compilation environment.
